A semiconductor device has a function of converting DC power supplied from a DC power supply into AC power to be supplied to an inductive load such as a motor or a function of converting AC power generated by a motor into DC power to be supplied to a DC power supply. In order to accomplish these conversion functions, the semiconductor device includes a semiconductor element having a switching function to perform power conversion from DC power to AC power or from AC power to DC power by repeating conduction operation and interruption operation,
In a semiconductor device, an insulating substrate having a wiring pattern formed thereon is bonded on a heat dissipating substrate through solder, and a semiconductor element is mounted on the wiring pattern of the insulating substrate. The semiconductor element has electrodes on the front and back surfaces. The back surface electrode is connected to the wiring pattern on the insulating substrate, and the front surface electrode is connected to the wiring pattern on the insulating substrate through the wire. In high-power semiconductors used for railroads, a plurality of insulating substrates are mounted so as to cope with a large current.
In recent years, the current density of a semiconductor device has increased. In particular, since a semiconductor element using SiC (silicon carbide) have a higher operating temperature than Si (silicon), a larger current can flow in the semiconductor element. If the current density of the semiconductor device increases, the amount of current flowing in one semiconductor element increases, so that the amount of heat generation increases. There is a problem in that, due to thermal expansion and contraction accompanying the increase in heat generation, a bonding layer bonding the back surface electrode of the semiconductor element and the wiring pattern of the insulating substrate is deteriorated, or bonding reliability between the front surface electrode of the semiconductor element and the wire is deteriorated.
In addition, in the case where the area of a semiconductor device is required to be reduced and wires are applied to the bonding between the front surface electrode of the semiconductor element and the wiring on the insulating substrate, there is a problem in that, the region of the wiring pattern on the insulating substrate is not sufficient, a sufficient number of wires cannot be bonded. Therefore, the front surface electrode of the semiconductor element and the wiring pattern on the insulating substrate need to be bonded with plate-shaped lead electrodes.
PTL 1 discloses a semiconductor device configured to include a lead frame having a die pad mounting a power semiconductor element and an external lead terminal, a plate-shaped metal piece electrically connecting at least between an electrode of the power semiconductor element and an external lead terminal or between the electrode between the power semiconductor element and an electrode of a control element, and a sealing resin sealing the power semiconductor element, the control element, and the metal piece.